European Patent No. 574,630 discloses a method of generating a private colourmap for a window in a windowing display system of the type having storage locations for storing a colourmap which determines the colours displayed in the system corresponding to particular pixel values, and means for generating a shared colourmap by assigning screen colours to pixel values dynamically as the screen colours are required by tasks using the system, and which system allows at least some of the windows to have a private colourmap which can be copied into the storage locations when the corresponding window is activated.
EP 574,630 discloses overwriting a selected portion of a copy of the shared colourmap with a user-determined colourmap of the same size as the selected portion to form a modified colourmap; and copying the modified colourmap into an area of storage assigned to the private colourmap for the window.
EP 574,630 does not take into account the fact that, not only may a window require a number of user-determined colours to display, for example, an image, the window may also need to display widgets, such as buttons, forming a user interface within the window in distinctive user-defined colors.